VIENNA (Reuters) - A nuclear-armed Iran would cause a regional arms race and make Tehran more isolated and vulnerable, according to a former Iranian negotiator who argues that the Islamic state is not seeking to build nuclear bombs.

Israel and the United States suspect Iran is developing a nuclear arms capability and have not ruled out military action to prevent it from obtaining such weapons of mass destruction.

Iran says it is only seeking nuclear energy. But its refusal to suspend atomic activity which can have both civilian and military applications, and its lack of openness with the U.N. nuclear agency, have drawn tough Western punitive measures.

Former nuclear negotiator Hossein Mousavian, now a visiting scholar at Princeton University in the United States, said Iran recognizes that if it were to become a nuclear weapons state Russia and China would join the United States and "implement devastating sanctions that would paralyze the Iranian economy."

Moscow and Beijing have backed a series of U.N. Security Council sanctions resolutions against Iran since 2006. But they have criticised tougher unilateral steps by Washington and the European Union targeting Tehran's vital oil exports.

"Based on Iranian assessments, the possession of nuclear weapons would provide only a short-term regional advantage that would turn into a longer-term vulnerability," Mousavian wrote in the National Interest, a foreign policy journal.

Mousavian held his post before conservative President Mahmoud Ahmadinejad took over from his reformist predecessor Mohammad Khatami in 2005.

Swedish Foreign Minister Carl Bildt, tweeting Mousavian's article, said "these points of view by a very well informed person are worth noting". Sweden is a member of the 27-nation EU, which has ratcheted up the sanctions pressure on Tehran.

Most Iranian politicians believe that having nuclear weapons would be an obstacle for Tehran's access to technological cooperation with developed countries, Mousavian said in the article headlined "Ten Reasons Iran Doesn't Want the Bomb".

"They do not want to see Iran come under the kind of extreme international isolation levied against North Korea," he said.

The allegation that Iran could use nuclear weapons, if it acquired them, against the United States or Israel "makes no rational sense," Mousavian said.

"Any provocation by Iran against two states that possess thousands and hundreds of nuclear weapons respectively would result in Iran's total annihilation," Mousavian said.

Israel is widely believed to have the Middle East's only atomic arsenal but neither confirms nor denies this under a "strategic ambiguity" policy to deter Arab and Iranian foes. (Reporting by Fredrik Dahl, Editing by William Maclean)

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